1. Technical Field
The embodiments herein generally relate to communication systems and techniques and particularly relate to multi carrier modulation systems such as Orthogonal Frequency Division Multiplexing (OFDM) type communication system and method. The embodiments herein more particularly relate to a method for reducing out of band (OOB) radiation or components and peak to average power ratio (PARR) in OFDM type communication system and method.
2. Description of the Related Art
Orthogonal frequency division multiplexing (OFDM) is a multicarrier modulation (MCM) technique that has been used in many conventional systems such as wireless local area networks (WLANs), long-term evolution (LTE) systems, digital video broadcast (DVB) and digital audio broadcast. Orthogonal frequency division multiplexing (OFDM) is a robust method for transmitting and receiving data over frequency selective channels.
In the current scenario, the orthogonal frequency division multiplexing (OFDM) is a mature and one of the most popular Multicarrier Modulation (MCM) techniques. Also, it is the main candidate for the physical layer of the Cognitive Radio (CR) networks. CR is a new method to satisfy ubiquitous demand for wireless services while the unlicensed spectrum is not sufficient. However, the most important shortcoming of OFDM-based CR systems is the high level of out of band (OOB) components that originate from simple fast Fourier transform (FFT)-based implementation.
In addition, the demand for ubiquitous wireless services has increased rapidly in the past years. Unfortunately, the vast majority of available spectrum resources have already been licensed and there is only limited bandwidth to set up new services. Further in CR, the unlicensed users are allowed to transmit and receive data over portions of a licensed spectrum, when the licensed users or primary users (PU) are inactive. To sense the inactivity of primary users and detect discontinuous bandwidth between active bands, or spectrum holes, the secondary users (SU) need to sense the spectrum. Because of the discontinuous nature of inactive spectra and the ability of OFDM to utilize such spectrum, OFDM has been the main candidate for the implementation of physical layer of CR networks.
However, the most important drawback of OFDM based CR systems is the large OOB radiation that originates from the high level side-lobes of IFFT modulated subcarriers. These side-lobes cause unwanted interference among secondary users and also between secondary users and primary users. Therefore, the OOB radiation of OFDM has been a considerable issue either in conventional applications or in CR networks.
Several methods are available for OOB radiation reduction in OFDM systems. Further the insertion of guard bands at the borders of OFDM spectrum has been proposed in the existing art. The drawback of this approach is the less effective utilization of the bandwidth.
Hence there is a need to provide a method and system for achieving reduction of Out of Band (OOB) Radiation in Orthogonal Frequency Division Multiplexing (OFDM). There also exists a need to provide an effective method for the reduction of the PAPR and Inter-carrier Interference (ICI). Moreover, there exists a need to provide a method for use in the CR systems for effective utilization of the spectrum.
The abovementioned shortcomings, disadvantages and problems are addressed herein and which will be understood by reading and studying the following specification.